The present invention relates to heat-curable, elastomer-forming halopolymer compositions and to cured elastomers prepared therefrom.
Several methods are known which enable halopolymers, such as halogenated polyolefins, to be vulcanized, cured, or crosslinked to form useful elastomeric products. For example, crosslinking has been effected by reacting the halopolymer with organic peroxides, polyfunctional amines, aliphatic polyazo compounds, or a combination of sulfur, a Group II metal oxide, and rubber vulcanization accelerator. Among these, the reaction with an organic peroxide has attained a prominent position in commercial applications due to the high degree of cure achieved thereby.
Nevertheless, the peroxide vulcanization of halogenated polyolefins, in particular, suffers from a number of significant problems, not the least of which are the high cost of the peroxide curing agents themselves and the high cost of the ester plasticizers which are typically used in such formulations. As a result, fully formulated chlorinated polyethylene, for example, has not been able to economically compete with other synthetic rubbers in its class, such as fully formulated polychloroprene.
Accordingly, workers in the art have embarked upon the search for an effective curing system for halopolymers, especially the halogenated polyolefins, which would not require the use of organic peroxides. An example of such a system has been described by A. A. Lontsov et al. in Kauch. Rezina 35, 30 (1976), wherein a combination of hexamethylenediammonium sebacate, sulfur, and magnesium oxide was reported to successfully crosslink chlorinated polyethylene.
It is a general object of the present invention to provide a non-peroxide curing system for halopolymers. More particularly, it is an object to provide an improved non-peroxide curing system for halogenated polyolefins which is superior to that described by Lontsov et al.